new program 24

Once a popular source of caviar, Atlantic sturgeon may soon be listed on the Endangered Species Act. New research shows that different types of Atlantic sturgeon may travel hundreds of miles from home, cross international waters, and mix with other sturgeon groups. Restoring Sturgeon populations will require protection wherever they swim.

Humans leave a mark on Earth that is detectable from space. By analyzing satellite images, scientists can measure the extent of deforestation, agriculture, urbanization, and other features. Satellite analysts estimate that humans directly affect 83 percent of our planet's land surface, leaving a dwindling percentage of land truly "wild." This huge influence is called the "human footprint."

The Pearl River delta near Hong Kong is a dramatic example of the human footprint. Humans have continuously occupied the region for thousands of years, and the region's cities are among the fastest-growing urban centers ever observed. Scientists use the same techniques illustrated for the Pearl River delta to study human-altered surface features around the world, thus mapping the global human footprint.

Most people think of urban sprawl as the construction of roads and buildings at a rate that exceeds population growth. Phoenix, Arizona, however, offers a contrasting model of sprawl. Its metropolitan area has grown more than 300 percent in recent decades, but its population has grown even faster. Since the mid-1980's, the city's population density has increased as people continue to move to the region even as the urban area's boundaries have grown more slowly. This trend is by necessity, since the water supply cannot feed an ever-expanding metropolitan area.

Ongoing studies of people with a rare congenital disorder called Williams Syndrome are revealing the genetic basis and brain activity behind their striking lack of social anxiety. The work, conducted by Karen Faith Berman and colleagues at the National Institute of Mental Health, is helping to unravel the complex biological influences on human social behavior.

Once a meandering river, the Mississippi is now constrained by development and levees lining its banks, leaving communities vulnerable during extreme high-water periods. The floods in May and June 2011 were the worst since 1927.